The invention relates to a two-piece barbed cable tie having improved bundling capabilities. The cable tie is suitable for use in an automated cable tie installation tool and can accommodate improved gripping of large or small bundles.
Plastic cable ties are well known in the art. There are two main types: one-piece plastic cable ties having an integral plastic locking device; and two-piece cable ties that incorporate a metal locking device insert. Examples of one-piece cable ties include U.S. Design Pat. No. D389,051 to Caveney et al. and U.S. Pat. No. 4,632,247 to Moody et al. Although most one-piece cable ties are manually assembled and tightened, certain versions can be used in an automated cable tie installation tool, such as the one disclosed in U.S. Pat. No. 4,632,247. Two-piece cable ties are primarily applied manually. Examples include U.S. Pat. No. 5,517,727 to Bernard et al., U.S. Pat. No. 3,457,598, U.S. Pat. No. 3,186,047 to Schwester et al., U.S. Pat. No. 6,560,822 to Caveney et al., and U.S. Pat. No. 3,457,598 to Mariani.
A representative low thread force conventional cable tie 10 of the two-piece type is shown in FIG. 1. Cable tie 10 is typically molded of thermoplastic to include a head 12 and a strap 14 as well as a number of standard features. Head 12 includes a strap accepting channel 18 defined by inner and outer walls. A metal locking device 22 is partially embedded at an angle within a barb receiving channel 20 of the cable tie head. The metal locking device 22 is situated at an angle so as to allow the tail end of strap 14 to be inserted through the strap accepting channel 18, but engaging the strap as it is pulled in a removing direction to prevent removal of the strap. Sometimes, a pocket 24 is formed below the metal locking device 22 to allow the mounted end of the metal locking member to rotate slightly in a direction towards the strap accepting channel 18. This construction enables the cable tie 10 to be secured around a large bundle 30 of cables as shown. Typically, the strap 14 has a generally solid cross-section in order to improve strap strength. However, because of the specific configuration, this type of cable tie is not preferable for securely fastening a very small bundle of cables. It also is not preferable for use in an automated installation tool.
Another conventional two-piece cable tie 10 is shown in FIGS. 2A and 2B. This one differs from the one in FIG. 1 by having a low profile head 12 with a strap accepting channel 18 oriented in line with the narrow dimension of the head 12. Additionally, strap 14 is provided with a preformed and bent strap neck 13 at the transition between the head 12 and strap 14 that, when relaxed, orients the strap at about 90 degrees relative to the head 12 and perpendicular to strap accepting channel 18. Although the neck 13 has a widened and reduced cross section 15 in the middle of the neck width, the peripheral lateral edges remain with substantial thickness, providing considerable remaining resistance to bending of the strap at the neck 13. Additionally, the strap accepting channel 18 is opened up at the inlet end 25 so that the strap end can be received within the profile of head 12 as shown. With this construction, a fairly small bundle of wires or cables can be securely bundled. However, because of the prebend, the substantial remaining rigidity of the cable tie at neck 13, and the geometry of the strap accepting channel 18, there is a limit to how small of an area can be snugly cinched up by a fully tightened cable tie as shown in FIG. 2A. This configuration also is not preferable for use with an automated installation tool.
Conventional two-piece cable ties may have some disadvantages. In many two-piece cable ties, the metal locking device (barb) can become inverted if a sufficiently high removal force is applied to the strap. Such inversion causes cable tie failure and is undesirable. Additionally, it is often difficult to sufficiently tighten a two-piece cable tie around a bundle without the cable tie rotating relative to the bundle or slipping axially along the bundle.
Although automated tools for installation of cable ties are known, such automated tools have used specially designed one-piece cable ties, such as ones shown in FIGS. 3A and 3B. An example of such an automated tool is disclosed in U.S. Pat. No. 4,623,247 to Moody et al. In FIG. 3A, a ribbon 38 of one-piece cable ties 40 is shown. Each cable tie 40 is mounted at its head 42 to strip portions 44 by a tab 46. The ties 40 are equally spaced with each tie's medial longitudinal axis being in parallel and each tie forming a right angle with strip portion 44. The one-piece ties 40 include head 42, strap 48 and an integrally molded locking device 43 that mates with wedge-shaped teeth 45 provided along a substantial portion of the bottom side of strap 48 as shown in FIG. 3B.
FIG. 4 shows a known automated tool 30 that includes a dispensing mechanism 32, a conveyance mechanism 34, and a remote tool 36. Dispenser mechanism 32 accepts the ribbon 38 shown in FIG. 3A and sequentially dispenses individual ties 40 to conveyance mechanism 34. The conveyance mechanism 34 delivers the individual ties to remote tool 36. Remote tool 36 then positions each tie 40 around a bundle of wire, tensions the tie 40 to a predetermined tension, and severs the tail of tie 40.